Pat
AI traffic is moving scenery, usually planes or boats or (rarely) ground vehicles in FS9, not under your direct control.
They are made to do this by means of traffic files which can be decompiled into 3 plain text component files:
aircraft.txt, airports.txt and flightplan.txt
These describe what moves from where to where.
Lee Swordy created Traffic Tools which allows users to compile the plain text files into a .bgl file which the sim understands.
He also developed AFCAD which is a programme allowing a user to modify airport data.
AI traffic requires a parking space at start and end points, plus taxiways and runways.
Often stock MS airfields don't have all this in place so AFCAD is used to create the data.
Sometimes existing airport data needs to be modified to suit the addition of AI traffic, e.g. to provide suitable realistic parking areas.
You can search the major FS sites for tutorials and in-depth discussions on this whole topic, which is not trivial and can take up the rest of your life if you really want to get into it.
The GNZLAP is an AI project for NZ General Aviation.
http://z11.invisionfree.com/nzff/index.php?showforum=17